Thermal interface resistance of Thermoelectric Generator (TEG) plays a vital role in power production. Improving surface finish of contact surfaces, applying pressure between the contact surfaces and use of Thermal Interface Material (TIM) are few methods of reducing thermal resistance and thereby improving the efficiency of TEG. There is a need to evaluate the influence of these methods and use them optimally for TEG system. Experiments were carried out to study the influence of parameters such as thermal conductivity of TIM, contact pressure, surface roughness and heat source temperature on the voltage and power outputs from TEG. Experimental results are validated with simulations using mathematical heat transfer model and COMSOLTM Multiphysics numerical model. Appreciable agreement is seen between the experimental observations and model outputs. Experimental and model results indicate 0.6 W/mK as optimum thermal conductivity for TIM material. Hence, use of costly TIMs like MWCNT (Multi Wall Carbon Nano Tube) and copper nanoparticles may not be required for the selected application. The contact pressure and surface roughness have appreciable influence when air is used as TIM. These factors have insignificant influence for TIMs with higher thermal conductivity. Increase in heat source temperature increases voltage and power output of TEG.